The control principle of a coffee percolator of this type is known for instance from German Patent No. 1,454,109. According to this known control procedure, the hot water feed to the brewing chamber is opened only when a brewing process is to be carried out. On starting operation of the coffee percolator after an extended rest period, the parts of the coffee percolator coming into contact with the hot water and the finished coffee are still cold, so that the coffee made in the first brewing process does not meet quality standards, that is, the coffee is too cold and its flavour is unsatisfactory. It may furthermore happen that after cleaning the percolator, residues of the cleaning water and possibly added detergents remain in the percolator so as to mix with the first coffee charge. In addition, the previously supplied water remains in the water heating container of the coffee percolator also during a rest period, so that it is cooled and degassed. The preparation of coffee with such stale water likewise results in a lowering of quality. These shortcomings are at present countered by discarding the first charge of the percolated coffee. This procedure is obviously rather uneconomical.